X-Y stages are used in professional microscopy because they permit a specimen slide fixed on it to be displaced with high precision and because the displacement in the two coordinates X and Y that define the stage plane can be controlled independently of each other. As a rule, such an X-Y stage comprises a stage plate consisting of three parts, viz. a base stage plate, an intermediate stage plate and an upper stage element. The upper stage element is mounted in a first guideway in the intermediate stage plate so as to be displaceable along a first axis X. The intermediate stage plate, in turn, is mounted in a second guideway in the base stage plate so as to be displaceable along a second axis Y. The two axes X and Y include an angle that differs from 0° and, as a rule, is 90°. Such an X-Y stage further comprises a mechanical, i.e. non-motorized stage drive, which essentially comprises two components: Firstly, the stage drive comprises an upper stage element drive with an upper stage element output link coupled to it for displacing the upper stage element. Secondly, the stage drive comprises an intermediate stage plate drive and an intermediate stage plate output link coupled to it. Using the upper stage element drive, one can define a first drive direction, and, using the intermediate stage plate drive, one can define a second drive direction. If, as commonly used, the stage drive is a coaxial control driving a shaft, the drive direction is the sense of rotation of the shaft, which, in a cross-sectional view, is either clockwise or counterclockwise.
Furthermore, such an X-Y stage may comprise first coupling means for coupling the upper stage element output link to the upper stage element. By means of the first coupling means, the upper stage element can then be displaced along the first axis in a first displacement direction, namely, as a function of the first drive direction. The drive direction, or the sense of rotation of the drive or shaft, thus defines the direction in which the upper stage element is displaced along the x-axis. Correspondingly, the X-Y stage may also comprise second coupling means for coupling the intermediate stage plate output link to the intermediate stage plate, by means of which coupling means the intermediate stage plate can be displaced along the axis Y in a second displacement direction as a function of the second drive direction.
The upper stage element may be designed in accordance with commonly used versions. In one configuration it may be designed as an upper stage plate, so that the X-Y stage altogether is composed of three stage plates located in different planes. The upper stage plate may be guided in a guideway on two sides.
In another common version, the upper stage element is designed as an upper stage strip. This can be combined with an object guide, which may be designed to be interchangeable. The upper stage strip is guided in a guideway permanently fixed to the intermediate stage plate, and the movement along the x-axis is effected by means of the driven upper stage strip along the guideway. The object guide itself is provided with means for receiving and holding a specimen slide with a specimen to be examined. This design is simpler that that incorporating an upper stage plate, because, instead of an upper stage plate held in two guideways, only an upper stage strip is required in which an object guide can be guided.
The base, intermediate and upper stage plates can be made available in different configurations. For examining specimens by transmitted light, one uses stage plates with apertures through which light coming from one side can pass through the specimen, and the light coming from the specimen, e.g., transmitted, dispersed or diffracted by it, is observed or detected on the other side. For the examination of a specimen by reflected light and the observation or detection of the light, e.g., reflected or, after excitation, emitted by the specimen, such apertures are not required, because the illuminating and observation ray paths are on the same side of the specimen. In this case the stage plates can be made without such apertures; alternatively, the apertures may be designed to be occludable, so that the stage plates are suitable for both ways of microscopical examination. For reflected-light work, it is sufficient if only one of the stage plates is occluded or without an aperture.
Microscopy is used in a variety of fields, which essentially belong to two categories, viz. biomedical applications and such in which aspects of material science are of prime importance. These two categories of applications differ by the preferred image orientations delivered by the microscope tubes employed. Tubes commonly used in biomedical applications provide an inverted image, which shows the specimen reversed both laterally (left and right sides changed) and vertically (top and bottom sides changed). Tubes used in material science show the specimens upright and true to side. Especially with higher microscope magnification, the field of view shows only a small segment of a specimen, so that the specimens need to be moved across the field of view by means of X-Y stages.
With some routine, the familiar image attitude provided by the tube, i.e., either the attitude used in biomedical applications or the one used in materials science, will enable the user to habitually manipulate the stage movement in such a way that the microscopical image of the specimen moves relatively to the field of view in the expected direction. If, however, a user, contrary to their habitual procedure, fits a tube with the image rotated by 180°, he or she will have to readapt to the stage movements required, a nuisance that will impede and slow down the microscopy jobs.
Since microscope tubes—especially such with practical and ergonomic functions appreciated by users, as, e.g., adjustable viewing heights or viewing angles—are designed according to sophisticated optical and structural concepts, they cannot be readily converted to offer both image orientations. Therefore, if a tube with a particular image orientation is preferred, e.g., for ergonomic reasons, either the user in the biomedical field or the user in materials science will face the problem of counterintuitive specimen shifting with the stage.